You may remember that about six months ago, Elon Musk tweeted that he foresaw a set of options for the upcoming Tesla Roadster, which would replace the rear seats with equipment for a rocket propulsion system developed by SpaceX. Musk first described the system as follows: "Greatly improves acceleration, top speed, braking and cornering" and follow up with "Maybe they'll even allow a Tesla to fly …" Now it seems he pushes this last bit even more. It's kind of a word. I mean, the word "nuts" is pretty relative when we're talking about a car with a reaction control system similar to a spacecraft, so keep that in mind. But you can see where the head is with this tweet: On this basis, it seems that it is really more excited by the flying / hovering part than anything else. He also talked about it in November, with a small hedge:

Not to say that the special upgrade pack of the next generation * will * fly over quickly, but maybe … Certainly possible. Just a security question. Rocket technology applied to a car opens up revolutionary possibilities. – Elon Musk (@elonmusk) November 19, 2017

It's worth remembering that the basic idea of ​​using some kind of reaction control jets on a car is not really a new idea, as such, at least to improve handling and even security. Why, I proposed such a system in 2012, and real established companies like Bosch even prototyped jets of cold gas traction and motorcycle safety improvement systems. I think it's possible to do something like that, especially if you own a rocket company, as we know.

You see, I thought you would use them for these kinds of thingsMore

The types of thrusters Elon seems to consider are the so-called cold gas thrusters. They have been used to help spacecraft to navigate and maneuver themselves for decades. They are called "cold gas" thrusters because nothing is ignited, it's just gas stored at high pressures that are broken down into controlled bursts to provide flares.

It is essentially the same technology as the fire extinguisher used by the fictional Wall-E robot to maneuver in space.Elon suggested The cold gas thrusters he thinks should use compressed air as a propellant, which means that an on-board compressor could be used to fill / refill the high-pressure propellant tanks. Even then, the amount of thruster needed to move a car over 3,000 pounds means that in the available area occupied by the tanks, you would measure how much time you could spend in seconds before the tanks were required. to be recharged.

Now, if we're talking about very short controlled bursts of cornering, grip, and maneuverability, that's probably fine, but Elon seems to have other goals in mind, as suggested by this Twitter feed: Ah. He always wants to fly. You see, that's the problem here. The basic idea of ​​a cold gas reaction control system for a sports car is really compelling and exciting, and could present real and real benefits. Creating a car capable of jumping a dozen feet in the air for about ten seconds is, well, a little silly.Elon is sometimes so frustrating to be hooked to the hovering / hopping part. He has a good concept, but he is obsessed with the stupid bullshit he saw in a movie he finds cool. That's why the X model ended up with these cool but complicated and inconvenient Falcon doors instead of a useful, much cheaper, sliding door, etc., and that's also why the Roadster can include an option for your car to get on a picnic table, then stay stuck there for half an hour because it compresses more air to get off. Some people have already done the math to determine the flight time that such a system could give:

Looking at my semi-written article – Fill the back seat with COPV – 140L of nitrogen at around 300 bar
~ 50 kg. A specific impulse ~ 50 means that to obtain 1 g of acceleration on a car of 2000 kg is 4 kg / s – 10 seconds of thrust.
So, not so unrealistic.- Scott Manley (@DJSnM) January 10, 2019

That seems pretty plausible: about 10 seconds. Others have done similar calculations and obtained even shorter results: Well, suppose 50 kg of nitrogen with an ISP of 60, pulled from a Roadster of a total mass of nitrogen of 1350 kg … One gram of acceleration would apply at 22.2 m / s delta V … 22.2 m / s / 9.807 m / s ^ 2 = ~ 2.26 s About two and a quarter seconds. So you can float the car as long, if the thrusters allow to maintain the balance of the car. So, a little more than two seconds. Everyone has to guess what the specifications and capabilities are here, but it's safe to say that whatever the system is, there's only enough room left for enough fuel for very high jumps. , very short. big question: who the hell wants that? What are you going to do with a car that can go up a few feet for a few seconds, then land? Skip control from time to time? Trying to impress lowriders? Jump quickly over a possum on the road? I mean, it would not be a flying car. In the best case, it would be a hopping car, even less demanding than a flying car. And we have not even considered the cost of such an option. Cold gas thrusters are not particularly complex, but the pressure vessels used to store the gas are. Elon describes an "overpacked composite pressure vessel" that would be expensive and subject to numerous safety tests, as any wreckage that could damage the ship would quickly become a bomb. It's frustrating to see Musc adopting a truly interesting idea – apply reaction control jets to the car handling – but then push it to its most spectacular and useless application. No one wants a car that can skip unnecessarily for very short jumps. Unless you're superstitious enough and concerned enough about your mother's spine for refuse to drive on cracks, I do not see what potential use the thrusters would have. I turned to Tesla for comment, but, shockingly, they do not comment on Elon's crazy Tweets. Probably a smart gesture.Read more